The invention relates generally to an opening roller unit of an open-end spinning device and more specifically to such a unit wherein the card clothing includes a helical groove, a number of ridges between the courses of the groove, and saw teeth cut into the ridges by a series of transverse cuts, as well as annular collars on the ends of the card clothing.
Opening roller units of open-end spinning devices, which are used for opening slivers supplied to them, are well known in the art to which the present invention relates. One kind of opening roller is known from German Patent Publication No. DE 29 04 841 A1, whose card clothing includes a saw-toothed wire wound on the roller body of the opening roller. In such a case the saw-toothed wire can be wound on the cylindrical surface of the opening roller, or it can be inserted into a helical groove. In practice, the end areas of the saw-toothed wire are not provided with teeth but are instead used for fixing the saw-toothed wire in place on the roller body, typically by pushing the ends into a depression in the helical groove.
German Patent Publication No. DE 31 23 480 C2 discloses an opening roller unit consisting essentially of a base body and a ring, wherein the ring is connected, and fixed against rotation, to the base body. A saw-toothed wire set into a helically circulating groove is wound on the outer circumferential surface of the ring. In place of sawteeth, the ring can be alternatively equipped with individual needles inserted into bores. The ring of the opening roller is embodied with annular collars arranged at the sides of the wound-on saw-toothed card clothing. Because the ring can be removed from the base body, it becomes possible to clean the area between the bearing housing and the opening roller relatively easily without elaborate disassembly of the opening roller unit.
German Patent Publication No. DE 44 11 735 A1 also discloses an opening roller of an open-end spinning device, which comprises a base body and cylindrical card clothing supported with integrated annular collars. The design is intended to permit simple mounting and dismounting, such as for maintenance, as well as for uncomplicated cleaning of the opening roller unit. The card clothing placed on the card clothing support consists of a saw-toothed wire wound on the outer circumference, or of rows of helically-arranged needles, which have been pushed into bores.
The saw-toothed wire of known opening rollers is generally not wound completely up to the annular collars in the edges of the card clothing, or, in some arrangements, the section of the wire near the annular collars has no teeth, as can be seen in FIG. 2 of German Patent Publication No. DE 29 04 841 A1. Regardless, in such arrangements there is a “free” space, in which no teeth are provided, between the area in which there are teeth and the annular collar. The width of this free space can here be greater than the distance between the rows of teeth over the width of the working area, and the distance between the teeth is called a tooth gap. Such a free space can be clearly seen in the respective FIG. 1 of DE 29 04 841 A1 or DE 31 23 480 C2, for example.
An opening roller is known from DE 35 15 153 C2, wherein the teeth have been cut out of the outer circumference of the sleeve constituting the card clothing. In order to form the teeth, at least one groove, which substantially circulates helically in the circumferential direction, and several cuts that extend in a substantially axial direction, have been cut. Prior to making the cuts, and perhaps even prior to cutting the helically circulating groove, the sleeve is subjected to a surface treatment process, such as hardening, for example. A particularly high wear resistance and true operating consistency of the opening roller can be achieved when a toothed card clothing is produced in this manner from a hardened sleeve.
With opening roller units of this type, the saw-toothed card clothing unit is arranged between two separate components, called annular collars, and is fixed in place by them. In accordance with the disclosed prior art, the teeth are always completely formed up to the edge of the card clothing unit.
It is furthermore customary to reduce the height of the teeth in the edge area of the card clothing. In this manner the danger of damage to the sawteeth in the edge area of the card clothing can be reduced as long as the card clothing is not yet enclosed by annular collars.
If the fiber material of the sliver is not fed to the opening roller at sufficient thickness and evenly distributed across the width of the roller up to the annular collars, it is possible that, in areas in which no material is fed and there is therefore no seal against the ambient air, air is aspirated through the tooth gaps at an increased flow speed, because of the vacuum pressure in the rotor housing of the open-end spinning device as compared with the circumferential speed of the opening roller. While this can occur at any place across the working width where an insufficient amount of fiber material is supplied, the problem is limited to a large extent to the edge areas. If the above-described free spaces exist in the edge area, the aspirating effect is particularly strong. Because of the increased air flow, fiber material which has not yet opened, or which has been opened insufficiently, is aspirated through the free spaces and carried along. In this manner, fiber material can reach the spinning rotor without having been opened, which can interfere with the yarn production process at the spinning rotor. For example, in such situations, the yarn leaving the spinning rotor can have undesirable imperfections in the form of undrafted parts.